Add support for const and async trait bounds

Author: compiler-errors

crates/parser/src/grammar/generic_params.rs

@@ -157,6 +157,16 @@ fn type_bound(p: &mut Parser<'_>) -> bool {
                     p.bump_any();
                     p.expect(T![const]);
                 }
+                // test const_trait_bound
+                // const fn foo(_: impl const Trait) {}
+                T![const] => {
+                    p.bump_any();
+                }
+                // test async_trait_bound
+                // fn async_foo(_: impl async Fn(&i32)) {}
+                T![async] => {
+                    p.bump_any();
+                }
                 _ => (),
             }
             if paths::is_use_path_start(p) {

crates/parser/test_data/parser/inline/ok/0211_async_trait_bound.rast

@@ -0,0 +1,43 @@
+SOURCE_FILE
+  FN
+    FN_KW "fn"
+    WHITESPACE " "
+    NAME
+      IDENT "async_foo"
+    PARAM_LIST
+      L_PAREN "("
+      PARAM
+        WILDCARD_PAT
+          UNDERSCORE "_"
+        COLON ":"
+        WHITESPACE " "
+        IMPL_TRAIT_TYPE
+          IMPL_KW "impl"
+          WHITESPACE " "
+          TYPE_BOUND_LIST
+            TYPE_BOUND
+              ASYNC_KW "async"
+              WHITESPACE " "
+              PATH_TYPE
+                PATH
+                  PATH_SEGMENT
+                    NAME_REF
+                      IDENT "Fn"
+                    PARAM_LIST
+                      L_PAREN "("
+                      PARAM
+                        REF_TYPE
+                          AMP "&"
+                          PATH_TYPE
+                            PATH
+                              PATH_SEGMENT
+                                NAME_REF
+                                  IDENT "i32"
+                      R_PAREN ")"
+      R_PAREN ")"
+    WHITESPACE " "
+    BLOCK_EXPR
+      STMT_LIST
+        L_CURLY "{"
+        R_CURLY "}"
+  WHITESPACE "\n"

crates/parser/test_data/parser/inline/ok/0211_async_trait_bound.rs

@@ -0,0 +1 @@
+fn async_foo(_: impl async Fn(&i32)) {}

crates/parser/test_data/parser/inline/ok/0212_const_trait_bound.rast

@@ -0,0 +1,34 @@
+SOURCE_FILE
+  FN
+    CONST_KW "const"
+    WHITESPACE " "
+    FN_KW "fn"
+    WHITESPACE " "
+    NAME
+      IDENT "foo"
+    PARAM_LIST
+      L_PAREN "("
+      PARAM
+        WILDCARD_PAT
+          UNDERSCORE "_"
+        COLON ":"
+        WHITESPACE " "
+        IMPL_TRAIT_TYPE
+          IMPL_KW "impl"
+          WHITESPACE " "
+          TYPE_BOUND_LIST
+            TYPE_BOUND
+              CONST_KW "const"
+              WHITESPACE " "
+              PATH_TYPE
+                PATH
+                  PATH_SEGMENT
+                    NAME_REF
+                      IDENT "Trait"
+      R_PAREN ")"
+    WHITESPACE " "
+    BLOCK_EXPR
+      STMT_LIST
+        L_CURLY "{"
+        R_CURLY "}"
+  WHITESPACE "\n"

crates/parser/test_data/parser/inline/ok/0212_const_trait_bound.rs

@@ -0,0 +1 @@
+const fn foo(_: impl const Trait) {}